2023年广东河源4.3级和东源4.5级地震余震分布及震源机制解特征  

The Aftershock Distribution and Focal Mechanism Solutions Characteristics of the Heyuan MS4.3 and Dongyuan MS4.5 Earthquakes in Guangdong in 2023

作　　者：姜喜姣 林庆西 陈修吾 朱腾 梁明 JIANG Xijiao;LIN Qingxi;CHEN Xiuwu;ZHU Teng;LIANG Ming(Guangdong Earthquake Agency,Guangzhou 510070,China;Key Laboratory of Earthquake Monitoring and Disaster Mitigation Technology,CEA,Guangzhou 510070,China;Key Laboratory of Earthquake Early Warning and Safety Diagnosis of Major Project,Guangzhou 510070,China)

机构地区：[1]广东省地震局,广州510070 [2]中国地震局地震监测与减灾技术重点实验室,广州510070 [3]广东省地震预警与重大工程安全诊断重点实验室,广州510070

出　　处：《华南地震》2023年第4期126-135,共10页South China Journal of Seismology

基　　金：地震监测、预测、科研三结合课题(3JH-202301026);震情跟踪定向工作任务(2023010108);广东省地震局青年地震科研基金(重点实验室开放基金)(GDDZZ202306)共同资助。

摘　　要：2023年2月11日,广东省河源市源城区发生4.3级地震,短短25天之后,东源县又发生4.5级地震。两次地震均位于新丰江库区,为了深入研究主震震源特性、余震序列空间分布以及水库诱发地震的特点和成因机理,文中分析了两次地震的余震分布特征,并利用gCAP方法和FOCMEC方法反演了主震的震源机制解。结果显示:河源4.3级地震是一次正走滑型地震事件,余震分布呈椭圆形,P轴方位为NW向,倾伏角较为直立,与峡谷及大坝区的应力场特征一致,判断其可能受控于多条断裂,并受水体重力影响,是一次正常的应力释放过程。东源4.5级地震发震于库盆西侧区域,是一次左旋走滑型地震,结合余震序列NNW—SSE向的线性展布特征,判断其发震断层走向为SSE向,倾角近直立;P轴方位为NWW向,倾伏角近水平,这和锡场区西侧应力场特征一致。库盆西侧是自2019年以来发生显著地震活动的新震区,和相邻的锡场区具有众多相似性,判断两个区域可能存在同一条隐伏的“北45o西向的顺河断裂”,由于库水渗透活动自北向南延伸,从而诱发锡场区和库盆西侧接连发生较强的地震活动。两个区域均处于早期孕震阶段,结合峡谷及大坝区的老震区特点,需重点关注两个新震区未来的应力场变化特征以及强震活动。On February 11th,2023,an M S4.3 earthquake occurred in Yuancheng District,Heyuan City,Guangdong Province.Just 25 days later,anM S4.5 earthquake occurred in Dongyuan County.The two earthquakes were both located in the Xinfengjiang reservoir area.In order to study the source characteristics of the main shock,the spatial distribution of aftershock sequences,and the characteristics and mechanism of reservoir-induced earthquakes,this paper analyzes the distribution characteristics of the aftershocks of the two earthquakes,and uses the gCAP and FOCMEC methods to invert the focal mechanism solution of main shocks.The results show that Heyuan M S4.3 earthquake is a positive strike-slip earthquake event,and the distribution of aftershocks is elliptical.The orientation of the P-axis is NW direction,and the pitch angle is relatively vertical,which is consistent with the stress field characteristics of the canyon and dam area.It is judged that Heyuan earthquake may be controlled by multiple fractures and affected by water gravity,which is a normal stress release process.The DongyuanM S4.5 earthquake occurred in the western area of the reservoir basin,which is a left-lateral strike-slip earthquake.Combined with the linear distribution of the aftershock sequence in NNW-SSE direction,it is judged that the strike of the seismogenic fault is SSE direction,and the dip angle is nearly vertical.The orientation of the P-axis is NWW direction,and the pitch angle is nearly horizontal,which is consistent with the characteristics of the stress field on the west side of the Xichang area.The west side of reservior basin is a new seismic area with significant seismic activity since 2019,and has many similarities with the adjacent Xichang area.It is judged that there may be the same concealed"North 45ºwestward trending along the river fault"in the two regions.As the seepage activity of reservoir water extends from north to south,it induces a series of strong seismic activities in the Xichang area and the west side of the reservoir basin.Bot

关 键 词：河源4.3级地震 东源4.5级地震 余震分布 震源机制解 FOCMEC方法 gCAP方法 

分 类 号：P315.3[天文地球—地震学]